In general, various types of electronic devices such as a smart phone or a tablet PC may record and store important data such as an Operation System (OS) or a file system in a non-volatile memory.
The nonvolatile memory may be various memories such as a Secure Digital (SD) card, a Universal Flash Storage (UFS) card, and an embedded Multi Media Card (eMMC).
For example, the eMMC, which is a large-scale storage medium such as 32 GB, 64 GB, and 128 GB, may record and store data in an NAND flash memory which is a last stage.
Recently, a manufacturing process of a non-volatile memory such as the flash memory has changed to a fine process, and, furthermore, as several bits are recorded and stored in one cell in the flash memory, maintainability of the stored data becomes weak.
When only an operation of reading data is intensively repeated after the important data such as the file system is recorded and stored in the flash memory, there is an increased risk of a value of the stored data being changed according to characteristics of the flash memory.
For example, when only one word line among several word lines configuring one block of the flash memory is intensively and repeatedly read, a threshold voltage (Vth) of another word line, which is not selected, gradually increases to cause a read disturb phenomenon in which data cannot be normally read. Since the read disturb phenomenon is a publicly known technology, a specific description thereof will be omitted.
When the read disturb phenomenon occurs, although data recording is impossible, an error for wrongly determining that the data recording is possible may occur. Therefore, for example, a problem in that important data such as a file system is wrongly recorded may occur.